TotalSecure Message Encrypter V2

ringzer0ctf

Task: Python2 encryptor implementing a hand-rolled Dual_EC_DRBG on NIST P-256 with two fixed points C/D; recover intercepted plaintext without the password. Solution: exploit the Dual_EC backdoor (D=d*C with tiny d=6002 found via BSGS) plus a decimal/binary length-mismatch that leaks the first keystream word verbatim in the ciphertext's leading digits, then advance the DRBG and XOR to decrypt.